Is there any reason why "poinsettia" became mispronounced?

This is a mispronounced word in English that I’ve never understood. Where do people get the idea that you can omit the letter “i” in this word? “Poinsettia” is often pronounced “poinsetta” or “pointsetta” and I even see it spelled that way sometimes. (The dictionary considers “poinsetta” a valid alternative pronunciation of the word).

But my question is: where does this come from? It’s a very unusual mispronunciation and there is no word I can think of in this language that is mispronounced in a similar way.

Are there any other words like this?